My cart is not empty when I take a new ticket

Hello. When I come to book a ticket (1 x ticket) and click on ‘add to cart’ and ‘view cart’ my cart isn’t empty. This happened a few hours ago as well, so I took ticket which empties the cart, and left it for a few hours. Now I’m returning to take another ticket, and I find that there are already another couple of items in my cart. Please do you know why this might be? Thank you. Dee